Field of the Invention
This invention relates to a helicopter with a multirotor structure and flight control.
Background of the Invention
The following definition for a multirotor aerial vehicle is:
“A multirotor or multicopter is a rotorcraft with more than two rotors. Multirotors often use fixed-pitch blades, whose rotor pitch does not vary as the blades rotate; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by each. Due to their ease of both construction and control, multirotor aircraft are frequently used in model and radio control aircraft projects in which the names quadcopter, hexacopter and octocopter are frequently used to refer to 4-, 6- and 8-rotor helicopters, respectively. Radio controlled multirotors are increasingly used as a low-budget option to create aerial photography and videos of sites and buildings.
Flight control in electronically controlled multicopters is achieved using a minimum of four control channels. One channel is usually labeled throttle and increases or decreases power to all motors evenly. This causes the aircraft to ascend or descend. The other three channels, labeled aileron, elevator, and rudder, control the roll, pitch, and yaw axes respectively. These three control inputs work by causing a change in aircraft attitude (tilt or direction). For example in an X4 configuration, forward tilt or pitch is controlled by increasing the speed of the two rear motors while decreasing the speed of the two front motors. Left or right tilt or roll is controlled by differences in the speed of the two right motors vs. the two left motors. The flight direction or yaw is controlled by changing the relative speeds of adjacent, counter rotating motors.” (Wikipedia)
A typical multirotor propulsion system may be of direct-drive configuration i.e. without reduction gear, this being the most common configuration, or of non-direct-drive configuration i.e. with reduction gear, this being a less common configuration. As long as a low lift capacity is required, as it is in model and radio controlled aircraft projects, the multirotor configuration has advantages relating to simplicity of structure and flight control and in reduced production costs, relative to the typical single main rotor helicopter configurations (e.g. Bell 206), or to tandem main rotor configurations (e.g. Chinook). However, at high lift capacity, the complexity of the multirotor vehicle, because of the higher number of high power propulsion systems and because of the significantly larger span and weight of the vehicle's structure required to support the propulsion systems, is considered a disadvantage relative to typical helicopter configurations.
It would obviously be advantageous to combine the advantages of a multirotor configuration relating to simplified structure and flight control with those of a typical helicopter having fewer main propulsion systems.